The present invention relates to a load-shifting device for an automotive vehicle. The device has a control element which acts on a setting member which determines the output of an internal combustion engine. The control element is adapted to be connected to an accelerator, and is controllable also by an electric setting drive which cooperates with an electronic controller.
Load-shifting devices, for instance load-shifting devices cooperating with carburetors or injection pumps, must assure optimum control of the internal combustion engine over the entire load range. This requires a complicated construction or complicated control of the load-shifting device in question. Thus carburetors, for example, have, in addition to the actual device for the forming of the mixture, additional devices such as thinning, starting, idling, accelerating, economizing devices etc. These devices complicate the construction of the carburetor and result in increased expense for parts since additional injection nozzles, pumps, special developments of the nozzle needles and separate air feeds are required, entirely aside from the stringent control requirements inherent in this.
Of particular importance in the case of load-shifting devices is control of the condition of the load upon idling, during which only a minimal output is delivered by the internal combustion engine but during which there may be present, particularly in the case of automobiles, load-consuming devices which require a high output, such as ventilators, rear window heating, air conditioning systems, etc. In order to take these potential demands on the output into account, the control of the load-shifting device between maximum and minimum idling positions is required and, upon failure of the control, an emergency idling position of the setting member or of the control element is to be assured.
Differing from the problem described above, load-shifting devices of the aforementioned type are, as a rule, used in cases where the accelerator and the setting member are electronically connected to each other. The accelerator is coupled to a driver and the latter is connected to the control element. Furthermore, a desired-value detection element associated with the driver and an actual-value detection element cooperating with the desired-value detection element and acting on the electric setting drive are provided. The electric setting drive is adapted to be controlled by the electronic controller as a function of the values detected. The electrical connections of accelerator and setting member to the interposed electronic controller make it possible to compare desired-value positions, determined by the accelerator and the driver coupled to it, with the actual-values indicated by the position of the control element and of the setting member and to check them for the presence or absence of plausibility conditions. Thus, in the event of the presence or absence of given plausibility conditions, there is the possibility of exerting a correcting action. The correcting action is accomplished by the electronic controller by controlling an electric setting drive, on the setting member. The setting drive, for instance, may be developed as a throttle valve or injection pump. An action by the electronic controller, in order to avoid wheel slippage upon starting, due to excessive output determined by the accelerator can be provided, and other automatic interventions into the load-shifting device are, for instance, conceivable in automatic shifting processes of a transmission or a speed-limiting control.